The effect of reagent structure and the medium on radical pair recombination in polymers

Abstract

Triarylcarbinols, the recombination products of ketyl and aminyl radicals identified by visible absorption spectra as relevant triarylmethane dyes, are formed during irradiation of poly(methyl methacrylate), poly(vinyl chloride), polystyrene and cellulose triacetate films containing substituted benzophenones and aromatic amines. Quantum yields of the reactions are determined. The features of reagents and polymer structures effect on the formation rates and yields of products are discussed. The reaction only proceeds in local zones of relatively large (∼ nm) size, as is found based on the analysis of quantum yield dependence on amine concentration. This stipulates the presence of magnetic-spin effects leading to a significant (by 10–20%) product accumulation rate decrease in poly(vinyl chloride) and polystyrene as external magnetic field is applied. A mechanism of significant photochemical post-effect in films produced from chlorine-containing solvent is suggested and kinetic description is proposed. The formation of dye at irradiated film treatment by HCl is diffusion limited. This allows using the reactions studied in the investigations of both slow and fast diffusion processes in polymers.